In general, a patternless lens edger measures the shape of an eyeglass frame or the shape of an eyeglass lens to be processed with a tracer, makes data corresponding to the measured shape, and grinds a blank lens according to the produced data by servo-controlling the positions of the axes fixing the blank lens to produce a lens having a desired shape. The patternless lens edger not only processes the overall shape of an eyeglass lens, but also forms a groove at the edge side of the lens for fixing a lens-fixing wire (grooving operation), chamfers the edge side of the lens (chamfering operation), and forms a bevel of a triangle shape at the edge side of the lens for securely fixing the lens to the groove line formed inside of an eyeglass frame (bevel forming operation). FIG. 1 is a perspective view for illustrating a conventional patternless lens edger, and FIG. 2 is a perspective view of the internal structures of a conventional patternless lens edger for illustrating the operation of the lens edger. As shown in FIG. 1, on the upper part of the patternless lens edger are formed an opening windows 2 for mounting an eyeglass lens inside of the lens edger and several control-switches 3 for controlling the lens edger. As shown in FIG. 2, the patternless lens edger includes a pair of lens fixing shafts 10 for clamping a blank eyeglass lens (not shown) to be processed; a carriage 12 which rotatably fixes the lens fixing shafts 10 and moves the position of the lens fixing shafts 10; a lens rotation motor 13 for rotating the lens fixing shafts 10; a carriage movement axis 14 which is attached at one end of the carriage 12 for allowing a rotational movement of the carriage 12 around the axis 14 and a sliding movement of the carriage 12 in the longitudinal direction of the axis 14; a horizontal driving means 16 which is attached to the one side of the carriage 12 for slidably moving the carriage 12 in the longitudinal direction of the carriage movement axis 14; and a vertical driving means 18 which is attached to the other side of the carriage 12 for rotating the carriage 12 in the rotational direction of the carriage movement axis 14. Also, the patternless lens edger further includes a diamond grinding wheel 20 for grinding the eyeglass lens clamped by the lens fixing shafts 10 to a desired shape, and a groove forming member 30 for forming a groove at the edge side the lens.
In operation, a lens is clamped between a pair of lens fixing shafts 10, and the part of the lens to be grinded is directed to the diamond grinding wheel 20 by driving the lens rotation motor 13. The horizontal driving means 16 and the vertical driving means 18 moves the carriage 12 in the horizontal and vertical directions, so that the lens clamped by the lens fixing shafts 10 contacts with the diamond grinding wheel 20. Then the lens is grinded by rotating the diamond grinding wheel 20 in a high speed. After processing the overall shape of the lens with the grinding wheel 20, the carriage 12 moves so that the processed lens contacts with the groove forming member 30 for a grooving operation, a chamfering operation, or a bevel forming operation at the edge side of the lens. For an accurate and precise grooving operation, chamfering operation, or bevel forming operation, the curvature of the processed lens should be precisely measured with an apparatus for measuring lens curvature, and the movement of the carriage 12 should be precisely controlled according to the measured curvature during the grooving operation, chamfering operation, or bevel forming operation. If the curvature of the lens is not considered for these operations, the processed lens may not be accurately fitted into the eyeglass frame, and the lens having a groove, a bevel or a chamfered part may be undesirable in its shape.